The Hepatitis C Virus (HCV) NS3/4A serine protease is essential for viral replication and the formation of infectious viral particles, and thus has been considered as one of the most attractive targets for anti-HCV therapy. Due to poor fidelity of viral reverse transcriptase and RNA-dependent RNA polymerase, drug resistant mutations emerge rapidly against protease inhibitors.

The recombinant HCV NS3/4A protease mutant V36M is derived from its wild type (NCBI Accession: CAB46913) with a substitution of Val36 with Met. It is a 217 amino acid fusion protein with NS3 protease domain and a fragment of the NS4A protein fused to its N-terminus.